1. Field of the Invention
The present invention relates to a positive resist composition to be employed in a process for producing a lithographic printing plate or a semiconductor device such as an IC, a process for producing a circuit board for a liquid crystal display or a thermal head, and other photofabrication processes, and a pattern forming method utilizing the same. In particular, the present invention relates to a positive resist composition functioning by a radiation of a high energy such as a far ultraviolet light (including an excimer laser), an electron beam, an X-ray or a light irradiation and suitable for preparing a semiconductor integrated circuit, and a pattern forming method utilizing the same.
2. Description of the Related Art
In a manufacturing process for a semiconductor device such as an IC or an LSI, a lithographic fine working with a photoresist composition has been employed. With a recent progress in the level of integration of the integrated circuits, there is being required formation of an ultrafine pattern in a submicron region or a quarter micron region. Together with such trend, the exposing wavelength is getting shorter, from g-line to i-line and further to a laser light of a KrF excimer laser. At present, a lithography utilizing an excimer laser light constitutes an important working technology in this field, and a chemical amplification resist is employed as a resist material suitable for such excimer laser lithographic process.
A chemical amplification resist composition is a pattern forming material which generates an acid in an exposed area by an irradiation with a radiation such as a far ultraviolet light, and differentiating a solubility to a developer between an area irradiated with the actinic radiation and a non-irradiated area by a reaction catalyzed by such acid, thereby forming a pattern on a substrate. The chemical amplification resist composition has a high sensitivity and a high resolution and has an advantage capable of an image formation by a compound which generates an acid by a little irradiation with a radiation (hereinafter called a “photoacid generator”).
The chemical amplification resist composition can be classified into a three-component system constituted of an alkali-soluble resin, a photoacid generator, and a dissolution inhibiting compound, having an acid decomposable group, to the alkali-soluble resin; a two-component system constituted of a resin having a group that is decomposed by a reaction with an acid to become soluble in an alkali, and a photoacid generator; and a hybrid system constituted of a resin having a group that is decomposed by a reaction with an acid to become soluble in an alkali, a low-molecular dissolution inhibiting compound having an acid decomposable group, and a photoacid generator. In the positive chemical amplification resist of such two-component system, three-component system or hydrid system, there is executed a thermal treatment in the presence of an acid generated from a photoacid generator by an exposure, followed by a development to obtain a resist pattern.
In a lithography utilizing a chemical amplification resist, there is required a photoresist excellent in various characteristics such as a sensitivity, a resolution, a profile, a coating property, a heat resistance, a dry etching resistance, an adhesion, a substrate dependence, an environmental stability (for example a dimensional stability to a change in time after coating), and a depth of focus (for example a pattern forming property against an out-of-focus state in an irradiation with a radiation), and many methods for performance improvement with additives have been disclosed.
For example, JP-A No. 2001-109154 and JP-A No. 2002-296783 disclose a resist composition containing norbornane lactone. However such resist composition, containing norbornane lactone, is poor in solubility in a solvent, and may cause a development defect. Also a further improvement is desired in imaging performance such as a light width roughness (LWR).
Also JP-A No. 2002-212174 discloses a norbornane lactone compound of a specified structure. Also JP-A No. 2000-159758 discloses various resist compositions. However, there has not been found a resist composition capable of meeting the aforementioned requirements.